Loss of audio quality in Shotcut?

Help/How To
#1

Hi everyone,

I am new to Shotcut and I have a question re. audio. I am producing music tutorial video clips with main focus on sound quality.

Way of working:

  1. I use Reaper (music editing software) to edit the audio material in sync with the video. (Reaper is great for sound editing, but rather limited for video editing)

  2. After rendering from Reaper I load this video/audio clip in Shotcut to edit the video a bit.

  3. Then I export/render this video from Shotcut (as mp4).

When I playback this final export version then (no matter if VLC, Widows Media Player, iTunes or Youtube), I get the impression of slight loss in sound quality (especially high frequencies) compared to the audio track before editing in Shotcut - even though I have done no sound editing in Shotcut.
Also strange: filesize is only half as big as before editing in Shotcut.

Is it possible that Shotcut affects the audio track quality post video editing and rendering, without touching any sound editing options in Shotcut?

Do I have to adjust settings in Shotcut in a certain way to keep the audio quality exactly as before editing?

Hope I made myself clear, sorry English is not my first language.

Thanks for tips in advance!

BR,
Emil

#2

Very clear!

Simple answer - “Yes”.

Here is a VLC Tools:Codec Information from a video I made on Shotcut this afternoon.

Screenshot_20210407_230426
Screenshot_20210407_230426602Ă—679 58.2 KB

Sample Rate: 48000 HZ

With the Nyquist Limit (laws of physics) at F/2, that is at 24kHz, which means there has to be a “brickwall” filter somewhere below that, which means that somewhere in the 17+ kHZ you are going to start seeing roll-off.

1 Like
#3

There is an option in Shotcut to double that Sample rate, to 96 kHz, but will it be playable on YouTube etc? That, I do not know.

I would suggest you look at your before-Shotcut material and your after Shotcut, both, on the Codec Information of VLC and compare them.

Foe what you are attempting to accomplish, you may need to set Shotcut to a higher audio standard than most of us use.

#4

What was the audio bitrate of your source file? And what was the audio bitrate of your exported file?

1 Like
#5

That is the crunch.

The video I looked at in VLC had a theoretical bitrate of 3 Mbs, (48 K x 32 x 2) but the codec in Shotcut said 384 kbs, so somebody is inside that machine compressing for all they are worth (I hope those little electronic elves are well paid).

#6

Thanks @kagsundaram but my questions were directed at @emil_cress. :slightly_smiling_face:

#7

@kagsundaram
@DRM

Thanks for your quick replies, guys!
To be honest, I am a bit clueless technical-wise.

RENDER SETTINGS IN REAPER:

reaper render settings
reaper render settings711Ă—583 72.4 KB

#8

…continue

I was told by the forum software that as new user I am allowed to put only one pic per post. :slight_smile:

VLC codec information before/after (in German, but you will figure it out I guess):

BEFORE SHOTCUT EDIT:

vlc before shocut
vlc before shocut585Ă—599 52.5 KB

#9

POST SHOTCUT EDIT:

vlc post shocut 2
vlc post shocut 2581Ă—591 55.8 KB

Any ideas what to do best in this case?

Maybe it would be better if I do first the video editing in Shotcut and thereafter audio editing?

#10

44100 and 48000 is a close mismatch.

If it was an analog carrier, it would give you a 3900 Hz beat frequency distortion; I don’t know in digital.

#11

Need to add that I use only the audio recording from Reaper anyway, not the audio from the video recording.

#12

Is it possible to set Shotcut to 44100 then?

#13

I don’t know.
It it possible to set Reaper to 48000?

#14

Yes, it is. Maybe I should give it a try.
Thanks for the quick reply! :slight_smile:

#15

Are you hearing something like this, faint, as a distortion?

#16

As @DRM rightly noted, the kbps is very important, as it controls the compression. You may want to set that much higher in Reaper as well, say 384k perhaps.

If it was me, doing high fidelity audio, I would also set both Reaper and Shotcut to 96000 samples per second.

#17

That is the beat frequency between 44100 and 48000.

#18

Ouch!
No, nothing that harsh. It is very subtle, maybe even a illusion. Sounds like the higher frequencies of an accoustic guitar are slightly washed out, kind of “blurred” (if that makes sense in an audio context)

#19

Guess I will do some more experiments with different settings.

#20

Good!

That is what I would expect from your sample rates.
The extreme low-pass filter (“brickwall filter”) needed to keep the frequencies near, at and above one-half the sample rate away from the digitization will be rolling-off already at the overtones of the high notes of an acoustic guitar, and the filter plays absolute havoc with the phase fidelity at those frequencies.

96000 samples per second
384 kbps
minimum